‘Virtual pivot point’ in human walking: Always experimentally observed but simulations suggest it may not be necessary for stability

Schreff, Lucas; Haeufle, Daniel F. B.; Badri-Spröwitz, Alexander; Vielemeyer, Johanna; Müller, Roy

doi:10.1016/j.jbiomech.2023.111605

Cited by 4 publications

(5 citation statements)

References 24 publications

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“…Since VPP and R 2 were only calculated for the single support phase, it cannot be assessed reliably if these two participants have a VPP or not in the LOLA-like condition in the whole stance phase. In a simulation study, stable walking without VPP could be found [ 43 ]. Here, the horizontal GRFs are also not balanced around zero (positive integral) in the single support phase.…”

Section: Discussionmentioning

confidence: 99%

Walking like a robot: do the ground reaction forces still intersect near one point when humans imitate a humanoid robot?

et al. 2023

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Bipedal walking while keeping the upper body upright is a complex task. One strategy to cope with this task is to direct the ground reaction forces toward a point above the centre of mass of the whole body, called virtual pivot point (VPP). This behaviour could be observed in various experimental studies for human and animal walking, but not for the humanoid robot LOLA. The question arose whether humans still show a VPP when walking like LOLA. For this purpose, ten participants imitated LOLA in speed, posture, and mass distribution (LOLA-like walking). It could be found that humans do not differ from LOLA in spatio-temporal parameters for the LOLA-like walking, in contrast to upright walking with preferred speed. Eight of the participants show a VPP in all conditions ( R 2 > 0.90 ± 0.09), while two participants had no VPP for LOLA-like walking ( R 2 < 0.52). In the latter case, the horizontal ground reaction forces are not balanced around zero in the single support phase, which is presumably the key variable for the absence of the VPP.

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Section: Discussionmentioning

confidence: 99%

Walking like a robot: do the ground reaction forces still intersect near one point when humans imitate a humanoid robot?

et al. 2023

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“…Rather it seems that only the entire interaction of the musculoskeletal system and its perturbation affect the existence of the VPP. This perturbation could be found for the non-VPP gait of the simulation study [22].…”

Section: Plos Onementioning

confidence: 67%

“…In contrast to the experiments, but in analogy to the outlier, a simulation study showed stable walking without VPP was possible [22]. The horizontal GRFs were balanced around zero for the whole contact since steady-state walking was investigated.…”

Section: Has the Vpp A Fundamental Function For Upright Gait?mentioning

confidence: 88%

“…The next step after finding out whether a VPP exists or not is to find the reason for its (non-) existence. In former studies, it was assumed that the VPP is necessary for postural stability [1] or, in contrast, to increase locomotion efficiency [22]. In studies with exoskeletons it was found that if the control is based on the VPP model, walking is more energy-efficient, i.e.…”

Section: Future Considerationsmentioning

confidence: 99%

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Virtual pivot point: Always experimentally observed in human walking?

Vielemeyer,

Schreff,

Hochstein

et al. 2023

PLoS ONE

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A main challenge in human walking is maintaining stability. One strategy to balance the whole body dynamically is to direct the ground reaction forces toward a point above the center of mass, called virtual pivot point (VPP). This strategy could be observed in various experimental studies for human and animal gait. A VPP was also observed when VPP input variables like center of mass or ground reaction forces were perturbed. In this study, the kinetic and kinematic consequences of a center of pressure manipulation and the influence on the VPP are investigated. Thus, eleven participants walked with manipulated center of pressure (i.e. barefoot, backwards, with a rigid sole, with stilts, and in handstand compared to shoe walking). In all conditions a VPP could be observed, only one participant showed no VPP in handstand walking. The vertical VPP position only differs between shoe walking and rigid sole walking, there are no significant differences between the conditions in the horizontal VPP position and the spread around the VPP. However, it is conceivable that for more severe gait changes, walking without VPP could be observed. To further analyze this issue, the authors provide a VPP calculation tool for testing data regarding the existence of the VPP.

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“…These findings led Müller and colleagues to the assumption that the VPP is not a target variable of the control system. Variations in VPP height were observed in studies on humans walking with different trunk inclinations (Müller et al, 2017), in humans walking and running over visible and camouflaged curbs (Vielemeyer et al, 2019;Drama et al, 2020), and in simulation studies (Lee et al, 2017;Schreff et al, 2023) added to that hypothesis. On the other hand, simulations and experimental studies on birds showed that VPP control in combination with a pronograde trunk stabilizes both trunk and overall locomotion (Andrada et al, 2014;Andrada et al, 2015a;Müller et al, 2017).…”

Section: Differences To the Single Bipedal Vppmentioning

confidence: 97%

Positioning of pivot points in quadrupedal locomotion: limbs global dynamics in four different dog breeds

Andrada

Hildebrandt

Witte

et al. 2023

Front. Bioeng. Biotechnol.

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Dogs (Canis familiaris) prefer the walk at lower speeds and the more economical trot at speeds ranging from 0.5 Fr up to 3 Fr. Important works have helped to understand these gaits at the levels of the center of mass, joint mechanics, and muscular control. However, less is known about the global dynamics for limbs and if these are gait or breed-specific. For walk and trot, we analyzed dogs’ global dynamics, based on motion capture and single leg kinetic data, recorded from treadmill locomotion of French Bulldog (N = 4), Whippet (N = 5), Malinois (N = 4), and Beagle (N = 5). Dogs’ pelvic and thoracic axial leg functions combined compliance with leg lengthening. Thoracic limbs were stiffer than the pelvic limbs and absorbed energy in the scapulothoracic joint. Dogs’ ground reaction forces (GRF) formed two virtual pivot points (VPP) during walk and trot each. One emerged for the thoracic (fore) limbs (VPPTL) and is roughly located above and caudally to the scapulothoracic joint. The second is located roughly above and cranially to the hip joint (VPPPL). The positions of VPPs and the patterns of the limbs’ axial and tangential projections of the GRF were gaits but not always breeds-related. When they existed, breed-related changes were mainly exposed by the French Bulldog. During trot, positions of the VPPs tended to be closer to the hip joint or the scapulothoracic joint, and variability between and within breeds lessened compared to walk. In some dogs, VPPPL was located below the pelvis during trot. Further analyses revealed that leg length and not breed may better explain differences in the vertical position of VPPTL or the horizontal position of VPPPL. The vertical position of VPPPL was only influenced by gait, while the horizontal position of VPPTL was not breed or gait-related. Accordingly, torque profiles in the scapulothoracic joint were likely between breeds while hip torque profiles were size-related. In dogs, gait and leg length are likely the main VPPs positions’ predictors. Thus, variations of VPP positions may follow a reduction of limb work. Stability issues need to be addressed in further studies.

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‘Virtual pivot point’ in human walking: Always experimentally observed but simulations suggest it may not be necessary for stability

Cited by 4 publications

References 24 publications

Walking like a robot: do the ground reaction forces still intersect near one point when humans imitate a humanoid robot?

Walking like a robot: do the ground reaction forces still intersect near one point when humans imitate a humanoid robot?

Virtual pivot point: Always experimentally observed in human walking?

Positioning of pivot points in quadrupedal locomotion: limbs global dynamics in four different dog breeds

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